With the progress of advanced information society, numerous attempts to use optical technology with respect to the transmission, processing, and recording of information have been made. In such a situation, a material (a nonlinear optical material) exhibiting a nonlinear optical effect has been noted in the field of optoelectronics and photonics. The nonlinear optical effect is a phenomenon showing the nonlinear relationship between the electric field applied and the electrical polarization resulting from when the strong electric field (light field) is applied to a material, and a nonlinear optical material refers to a material that exhibits significantly such nonlinearity. As a nonlinear optical material using a secondary nonlinear response, a material which generates a second harmonic wave, a material that exhibits Pockels effect (primary electro-optic effect) causing refractive index changes in proportion to the primary of an electric field or the like are known. Especially, the application of the latter has been investigated as an electro-optic (EO) light modulation device or a photorefractive device. Further, it is expected to exhibit a piezoelectric and pyroelectric property, and also its application to various fields.
As a secondary nonlinear optical material, an inorganic nonlinear optical material such as lithium niobate or potassium dihydrogen phosphate has already been put into practical use and has been widely used, but recently an organic material which                1) represents a large nonlinearity,        2) has a fast response rate,        3) has a high optical damage threshold,        4) is possible to design a great variety of molecules, and        5) is excellent in manufacturing aptitude, etc. has been noted and thus its vigorous research and development toward the practical use has been made.        
However, for the expression of the secondary nonlinear optical effect, since it is necessary that the polarization induced by an electric field lacks inversion symmetry center and the nonlinear optical response group or molecule showing a nonlinear optical effect needs to be placed in a structure which lacks inversion symmetry, the organic compound having a nonlinear optical activity is roughly divided into a system (hereinafter referred to as “crystal system”) which was crystallized in the crystal structure which lacks symmetrical center and a system (hereinafter referred to as “polymeric system”) whose organic compound having a nonlinear optical activity was oriented by any means by dispersing or binding the corresponding organic compound having a nonlinear optical activity to the polymer binder.
It is known that the organic nonlinear optical material of the crystal system may exhibit very high nonlinear optical performance, but there are problems in that the production of large organic crystals necessary for devices is difficult, and the strength of the organic crystal is very brittle and damaged in the process of devices. In contrast, the organic nonlinear optical material of the polymeric system gives desirable properties such as useful film-forming properties, the mechanical strength when a device is produced by the polymer binder, and its potential for practical use becomes high and promising.
In order to place the nonlinear optical response group or molecule showing a nonlinear optical effect as in the structure which lacks inversion symmetry center as conventional techniques in the organic nonlinear optical material of the polymeric system, it is possible to introduce a nonlinear optical response group or molecule showing a nonlinear optical effect in the polymeric binder. For example, it has been widely used to orient the dipoles by an electric field. The orientation control by the electric field is referred to as “poling”, and the poled organic polymer is referred to as “an electric field oriented polymer (poled polymer)”. That is, this is a technique to align the dipole of the response group or molecule showing the secondary nonlinear optical effect by applying a high voltage at a temperature higher than the glass transition temperature of the base polymer, and then to freeze the orientation of the dipole by the electric field by cooling. For example, an electro-optical (EO) light modulator made in accordance with the present method is known
However, there is a problem that the dipole of the response group or molecule showing the secondary nonlinear optical effect oriented by poling causes the thermal relaxation of orientation over time, and concomitantly the nonlinear optical properties of a material become deteriorated.
Thus, for the organic nonlinear optical material of polymeric system, it is required to include an organic compound having high nonlinear optical activity and a polymer binder being capable of keeping the orientation state of the organic compound having implied nonlinear optical activity stable in addition to having high film forming properties, mechanical strength, and the like.
As for the organic compounds having the above mentioned nonlinear optical active, tertiary amine derivatives such as Disperse Red 1 (generally, abbreviated as DR1) or 4-(Dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (generally, abbreviated as DCM) are well known.
However, the organic compound itself does not have large nonlinear optical characteristics, and thus further improvement has been desired.
To solve this problem, the search for an organic compound having large nonlinear optical property has been actively carried out, and the effectiveness of an organic compound having tricyanofuran structure having a high electron-withdrawing property or an organic compound having a long π-conjugated bond group has been reported, but it is known that the organic compounds are decomposed and they do not withstand a practical use as an optical device in continuous driving in light wavelength (for example, 1.33 μm) that is intended to be actual driving (for example, see Patent Documents 1 and 2 and Non-patent Document 1).
Further, an organic compound having a tricyanopyrroline structure as a high electron-withdrawing group or an organic compound having a tricyanopyrroline structure and a long π-conjugated bond group has also been reported (for example, Patent Document 3 and 4), but light resistance was still insufficient. In addition, in the Non-patent Document 2, an organic compound having a tricyanopyrroline structure was disclosed, but it was described that the synthesis was not possible.
Meanwhile, as the polymeric binder, polymethylmethacrylate (in general, abbreviated as PMMA) has been studied most frequently, but the glass transition temperature of PMMA is as low as 100° C., and the orientation state of an organic nonlinear optical material of a polymeric system using PMMA a polymer binder is relaxed slowly even at room temperature, and the nonlinear optical performance becomes significantly deteriorated over time. Thus, it is known that PMMA may not withstand the practical use as a functional device (for example, see Non-patent Document 3).
To solve this problem, the search for the polymer binder instead of PMMA has been actively carried out, and the effectiveness of the polymer having higher glass transition temperature than that of PMMA such as polycarbonate, polyimide, polysulfone or the like has been reported (for example, see Patent Document 5), but there was a problem that in the case of using a polymer binder having this high glass transition temperature, the temperature of the heating required for the electric field poling will rise, or in the case of using the DR1 or DCM as an organic compound having a nonlinear optical activity, this low molecular compound was vanished or oxidized by sublimation.
In addition, in consideration of the solder mounting such as a printed circuit, it becomes exposed to the heating conditions of 230° C. or more even in a short time, and the problem such as sublimation or decomposition of low molecular compound becomes more remarkable.
Further, since the organic compound is exposed to harsh conditions that still higher electric field is applied to the heating at a high temperature during poling, it may be stable only by heating. But, there is not less cases that the compound will decompose under the conditions of heating or high electric field. However, it is difficult to clarify the molecular design that confers voltage stability to the organic compounds having a nonlinear optical activity, there is also little discussed with respect to voltage resistance and a tendency that large nonlinear optical activity is priority in molecular design of the same compound is strong. Therefore, in order to obtain a high orientation state without damaging the nonlinear optical activity of the material, it is not possible to search the poling condition such as temperature, electric field, time, and the like in turns. However, there has been a demand for a compound being fundamentally stable about poling conditions without a guarantee that there is no essential solution and suitable conditions are found.